In the present state of the art, viscous food liquids or products are frozen in containers of variable volume, from 250 ml., for example, for concentrated fruit juices to 10 or 20 liters for egg yokes, in containers of plastic or other materials, and even 30 to 50 liters for orange juice packaged in plastic bags.
Freezing foods in flake or chip form by the use of cooled cylinders or the like has not been adapted to the products considered. It is suitable only for liquids with slight viscosity, such as water, for example. Viscous food liquids and products are therefore treated with the technique of freezing in units.
Freezing in units of viscous food liquids and products, according to the present industrial practice, has several drawbacks.
In all cases, the product subject to freezing treatment is put in a package. Now, any packaging is burdensome and all the more so, the smaller the unit volume.
Further, freezing and thawing are slow. Thus, unit freezing of bags of orange juice of 30 to 50 liters requires a stay of 24 to 48 hours in cold storage, and that of eggs in containers about 48 hours. During these prolonged freezing periods, the food products run the risk of evolving and changing during these operations. In the case of thawing, an increase of the speed of the latter can cause overheating and a deterioration of the quality of the product, for example, if a thawing of a unit of soup with the usual cooking means is involved.
Further, it is necessary to thaw the entire unit because it is difficult to fragment it, which prevents the practical use of small amounts of the product. For the same reason, mixtures of products in the frozen solid state cannot be achieved, whereas this technique should be able to be used to make different proportions of products that are finished or to be transformed.